The way I make gold is by selling, booty grab, posting in forums frequently, and sometimes games.
Also! You can buy a cash card online here at Gaia or at a local game store. You can buy a few items that are at the Cash Shop and sell them at the marketplace for lots of gold! That's how I got most of my gold.
As for Booty Grab, you should go to the Gaia Aquarium Forum for Booty Grab. Or, you could join A Booty Grab guild.
Try to post in the forums frequently! Chatterbox is the best place to go. So go there and post, post, post!
I hope these tips help you